Assessing sexual behavior with self-report is essential to research on a variety of health topics, including pregnancy and infertility, sexually transmitted infections, and sexual health and functioning. Recent methodological research has provided new insights regarding the accuracy of self-reports of sexual behavior. We review these studies, paying particular attention to a promising new development: the use of computer-assisted assessments. The collection of sexual risk behavior data with computers has increased dramatically in recent years, but little is known about the accuracy of such assessments. We summarize the evidence, discuss methodological issues that arise in studies evaluating the accuracy of self-reports, and offer recommendations for future research.